This invention relates to a semiconductor electronic circuit, and, in particular, to a semiconductor electronic circuit which can generate high voltage pulses.
Circuit systems are known in which several circuit elements are connected in series in order to obtain a high voltage output. Prior art devices, in which a plurality of transistors are connected in series and their bases are driven simultaneously, are disclosed in JP-A-No. 52-19932, JP-A-No. 56-162543, JP-A-No. 60-51024, JP-A-No. 60-57724, etc. FIG. 2 illustrates a respective circuit construction of such devices.
In FIG. 2 transistors 1 and 2 are connected in series and resistors 3 and 4 are resistors short-circuiting the base and the emitter of each of the transistors . A driving signal is inputted through capacitors 5 and 6, respectively. The reference numeral 7 represents a driving signal source. The transistors 1 and 2 work as if they were a single transistor, one end of which is connected through a load resistor 9 with a voltage source terminal 8 and the other end of which is connected with another voltage source terminal 11. The output terminal is designated by 10 and in many cases voltage amplitude signals appearing there are used as the output.
By this circuit system it is possible to obtain a high withstand voltage owing to the superposition of many transistors. However, the operation speed of the circuit is slow, because it has no discharge path, in the case where the load is capacitive.
FIG. 3 indicates a method for resolving this problem. It is a so-called push-pull circuit construction, by which complementary transistors 12 and 13 are combined. The output terminal 10 is taken-out from the transistor
connection point, through which electric power is transferred to the load. By this circuit system it is possible to increase the working speed, but the withstand voltage of the transistor elements 12 and 13 should be raised, in order that the circuit can be used as a high withstand voltage circuit. Further, if each of the transistors 12 and 13 in FIG. 3 actually consists of a plurality of transistors, as is the case for the transistors 1 and 2 in FIG. 2, a high withstand voltage can be obtained. However, in the case where complementary transistors are used as in the circuit indicated in FIG. 3, it is difficult to balance the p and the n conductivity type and particular attention should be paid to how to drive the circuit. In addition, capacitors having a relatively large capacitance are used for coupling the signal source 7 with the base of the transistor, and fairly sophisticated techniques are necessary for fabricating high withstand voltage capacitors.